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Mozilla Foundation Security Advisory 2011-38

Title: XSS via plugins and shadowed window.location object
Impact: High
Announced: September 27, 2011
Reporter: Boris Zbarsky
Products: Firefox, Thunderbird, SeaMonkey

Fixed in: Firefox 6.0
  Firefox 3.6.23
  Thunderbird 6.0
  Thunderbird 3.1.15
  SeaMonkey 2.3


Mozilla developer Boris Zbarsky reported that a frame named "location" could shadow the window.location object unless a script in a page grabbed a reference to the true object before the frame was created. Because some plugins use the value of window.location to determine the page origin this could fool the plugin into granting the plugin content access to another site or the local file system in violation of the Same Origin Policy. This flaw allows circumvention of the fix added for MFSA 2010-10.